speciaon* - | department of zoology at ubcjankowsk/biol413-6-012615-speciatio… · speciaon* 2...
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Specia'on
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Specia'on
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"Wallace and Darwin’s great insight [natural selec5on as a factor in specia5on] only began the era of asking. The ‘mystery of mysteries’ had been solved, at least in rough outline; then came the task of elabora5on. The colleagues and successors of Darwin and Wallace have now been at it for more than a century and a quarter, and throughout most of that effort biogeography has been their paramount tool. The paFerns of species distribu5on have provided clues about the ways in which species originate, change, and diverge, and the ques5on how? has remained inseparable from the ques5on where?….The linkage between geographical circumstance and evolu5onary development is embodied in the very word ‘biogeography’."
-‐ David Quammen from Song of the Dodo
Specia'on
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Why study species and specia5on? What cons'tutes a "species" and how they arise ("specia'on") is fundamental to biogeography: 1) Recall that the geographic distribu'on of species (and their aEributes) is the fundamental unit of observa'on in biogeography. To collect and understand basic biogeographic data (i.e., distribu'ons) we must define what we mean by species 2) The role of geography in specia'on (or the lack thereof) is highly controversial and geographic aspects of species forma'on are an important unknown in biology 3) The geographic distribu'ons of species have played (and con'nue to play) important roles in understanding the process of specia'on
Specia'on
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Overview of this sec5on: 1) Species Concepts
2) Mechanisms of Specia'on 3) Geography of Specia'on
Specia'on
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Overview of this sec5on: 1) Species Concepts
2) Mechanisms of Specia'on 3) Geography of Specia'on
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1. Genotypic or Phenotypic Cohesion Species Concepts
Issues: How dis'nct must a group of individuals be to be declared a species? Some species have a tremendous amount of morphological (or gene'c) diversity across their range. Some'mes groups of individuals are iden'cal morphologically, but gene'cally differen'ated.
Morphological Species Concept: a species is a morphologically dis'nct group of individuals that has few or no intermediates when in contact with other such clusters (Mallet 1995).
Species Concepts
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Morphological differen'a'on of the yarrow (Achillea millefolium) along an eleva'onal gradient in the Sierra Nevada mountains of California
Lomolino et al. 2010 Eleva'on from which seed was collected (m)
Height of p
lants (cm
) Species Concepts
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winter wren !pacific wren!Toews and Irwin, Molecular Ecology, 2008 !
Cryp'c specia'on in Troglodytes wrens
Species Concepts
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Character displacement in Darwin’s finches Morphology of species is influenced by co-‐occurring species and resource use
Lomolino et al. 2010 Beak Depth (mm)
Rela've freq
uency (# of ind
ividual bird
s)
Species Concepts
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Divergence of monarch flycatcher popula'ons (Monarcha castaneiventris) on the Solomon Islands
east of New Guinea.
Lomolino et al. 2010
Species Concepts
2. Phylogene5c Species Concepts Issues: Which derived diagnos'c character states do we focus on? Requires reliable knowledge of evolu'onary rela'onships of species. Benefits: Can apply to asexual and sexual reproducing species
Phylogene5c Species Concept: a phylogene'c species is (1) a monophyle'c lineage, (2) derived through an evolu'onary process of descent from an ancestral lineage and (3) diagnosable through examina'on of character state transforma'ons (McKitrick & Zink 1988; Cracraf 1989).
Species Concepts
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Monophyle5c group: Descendants from a single common ancestor Paraphyle5c group: Does not include all descendants from single common ancestor Polyphyle5c group: Descendants that have mul'ple origins and do not share a common ancestor – an issue when species are described without gene'c data
Monophyle'c (share single common ancestor)
Paraphyle'c (do not include all descendants)
Polyphyle'c (mul'ple origins)
Species Concepts
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with 5me, reproduc5ve isola5on...
'me
2o contact
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Species Concepts 3. Biological Species Concept
Biological Species Concept (BSC): species are groups of interbreeding natural popula'ons that are reproduc'vely isolated from other groups (Mayr 1942, 1995). Most widely held concept for species delinea'on.
Species Concepts
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3. Biological Species Concept
Issues: How important is the dis'nc'on between actually or poten=ally interbreeding? How does one apply the BSC to species that are geographically isolated? How does one apply the BSC to species known only from fossils? The concept of reproduc've isola'on doesn’t make sense for asexual species.
Biological Species Concept (BSC): species are groups of interbreeding natural popula'ons that are reproduc'vely isolated from other groups (Mayr 1942, 1995). Most widely held concept for species delinea'on.